Total internal reflection ellipsometry for kinetics-based assessment of bovine serum albumin immobilization on ZnO nanowires

The properties of the ZnO-NWs were investigated by utilizing spectroscopic ellipsometry under TIRE configuration during real-time measurement of covalent BSA immobilization.

Optical Dispersions of Bloch Surface Waves and Surface Plasmon Polaritons: Towards Advanced Biosensors

The total internal reflection ellipsometry (TIRE) method was used for the excitation and study of the sensitivity features of surface plasmon polariton (SPP) and Bloch surface waves (BSWs) resonances. For the BSWs generation distributed Bragg gratings were formed on the tops of the substrates (BK7 glass substrate), which had six bilayers of ~120 nm SiO2 and ~40 nm TiO2 and 40 nm of TiO2 on the top. The SPP sample consisted of the BK7 glass prism and a gold layer (45 nm). Numerical calculations of the optical dispersions and the experimental TIRE data have shown that SPP resonance overtake the BSWs in wavelength scanning by a factor of about 17. However, for the ellipsometric parameters Ψ and Δ in the vicinity of excitations, the BSW sensitivity is comparable with SPP. The obtained resolutions were Δ S P P = 7.14 × 10 − 6 R I U , Ψ S P P = 1.7 × 10 − 5 R I U for the SPP and Δ B S W = 8.7 × 10 − 6 R I U , Ψ B S W = 2.7 × 10 − 5 R I U for the BSW. The capabilities of both surface excitations are discussed from the sensitivity point of view in the design of these advanced biosensors.

Treatment of Surface Plasmon Resonance (SPR) Background in Total Internal Reflection Ellipsometry: Characterization of RNA Polymerase II Film Formation

To deal with the general problem of biomolecule specific binding analysis, we have applied the technique of difference spectra to the surface plasmon resonance (SPR)-enhanced total internal reflection ellipsometry measurement. We suggest a three-step treatment of the SPR background that can easily be integrated with the usual measurement routine. First, making use of the difference spectrum in ellipsometric angle Δ, single peak footprints of the topmost layer are obtained that facilitate its sensitive detection during film growth. Subsequently, circumventing the need for explicit knowledge of the substrate properties, the difference spectra peaks can be used for the end-point analysis of a binding. Finally, tracking the binding effectivity of the analyte we determine the injection speed and analyte concentration windows needed for successful monitoring of the film growth. We demonstrate our approach on a comprehensive two-stage binding experiment involving two biologically relevant molecules: the C-terminal domain (CTD) of RNA polymerase II and CTD-interacting domain of one of its transcription factors, the Rtt103 protein.